Apparatus and process for making tape useful as a tire cap ply from greige fabric

ABSTRACT

An apparatus and process are used to make a ready-to-apply tape from greige fabric. This tape can be used as cap plies, breakers and reinforcement in the carcass of tires. The tape is made by dipping a greige mini-fabric which comprises a plurality of single end cords in a solvent-based cement. The cement, which comprises solvent and an elastomeric composition, is dried so that the majority of the solvent evaporates. The elastomeric composition remains, encapsulating the fabric, thereby forming the tape.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a Divisional of U.S. patent application Ser. No.10/651,363, filed Aug. 29, 2003.

FIELD OF THE INVENTION

The present invention relates to an apparatus and a process for makingtape which can be used as cap plies, breakers and reinforcement in thecarcass of tires, and in particular, an apparatus and process for makingsuch a tape from greige fabric. The tape can be produced to thedimensions of the application, such as a cap ply of a specified numberof ends.

DESCRIPTION OF THE RELATED ART

The tire industry has long had considerable interest in belted tireconstructions for reinforcing tires. An example of a tire reinforcementis described in U.S. Pat. No. 3,720,569 to Kimble. This reinforcement isformed by passing a plurality of cords in the desired spacedrelationship through an extruder. The cords may be coated with a rubberlatex in a multiple dip operation to form a unitary strip. Suchreinforcement constructions may offer the advantage of better roadstability and longer tread life in both radial and bias plyconstructions. However, such constructions are subject to belt-edgeseparation failures because the adhesion of the reinforcement to thetire rubber is inadequate.

Cap plies that envelop radial tire belts may be used to help minimizesuch belt-edge separation failures. Initially, cap plies were applied asa full width strip with an overlap splice. Experience has shown that thesplice could pull open during curing. In addition, there is a limitationon the extension of the belt, since the cap ply is applied over thebelt. Moreover, with this configuration, the same width of material mustbe applied across the whole belt. As a result of these limitations, anarrower cap ply tape was developed in the 1990's. This tape is spirallywound about the belt. Such a tape is made by slitting rubberized fabric.The width of the tape depends on the number of cords per inch, whichvaries according to the tire manufacturer. It was found that such a tapecan increase winding tension, as there is no splice. Also, such a tapecan be applied in extra layers at the belt edges to improve tireperformance. However, this process is dependent on severalprocesses/steps, i.e., weaving fabric, treating fabric to achieve goodadhesion to the calendered rubber, compounding rubber, skimming orcalandering the rubber onto the treated fabric and slitting therubberized fabric to specific widths. These are inherently highcost/labor intensive procedures. Because of the slitting step, there maybe cut cords on the edges of the tape, which may create edge fray.Consequently, such a process produces a fair amount of scrap material.Moreover, the tape so produced can be non-uniform, due to the possiblevarying number of single end cords in each strip. With each step thepotential for error and the additive variances requires allowance forexcessive tolerances in the tire building process. Finally, the additionof rubber to ensure good adhesion of the fabric to the tire rubber addsto the overall weight of the tire.

The process for making belt cord fabric is similar to the slit fabricprocess in that it includes treating fabric, with, for example, an rfldip to achieve good adhesion. However, the belt cord fabric differs insignificant ways: the weft cord is identical to the warp cord, thefabric is ready-to-use in the belt building process in that it does notrequire slitting, and the fabric does not require a rubberizing step.

Because of the inherent drawbacks in the slit rubberized fabric process,a process for the preparation of a cap ply tape from single end cordsusing a cross-head extruder has been developed. Such a process iscommonly known as the STEELASTIC® Cap Strip System, and is illustratedin FIG. 1. In the STEELASTIC® Cap Strip System, shown generally at 1, aplurality of cords 2 and rubber 3 are brought into a die head 4, wherethe cords are encapsulated by rubber to give a good adhesion to the tirerubber. A tape which comprises a plurality of rubberized single endcords is thus formed. The cords must be treated with aresourcinol-formaldehyde latex dip before they are brought into the diehead to ensure good adhesion to the rubber introduced in the extrusionstep.

The STEELASTIC® Cap Strip System provides improved uniformity ascompared to the slit rubberized fabric process, since there nopossibility of uneven slitting and hence there is exact control of thenumber of single end cords in the tape. Moreover, this process hasreduced scrap as compared to the slit rubberized fabric process, sincethere are no cut cords on the edges of the tape. In addition, longerlengths per roll of tape are possible with the STEELASTIC® Cap StripSystem. However, the extruder and the die heads used in this processrepresent a major capital investment. Moreover, the tape itself is stilldependent on a rubber compounding step and the addition/application ofrubber as a means to ensure good adhesion to the tire rubber compounds,hence increasing weight and cost. In addition, the STEELASTIC® Cap StripSystem requires above ambient pressures and temperatures. Therefore,there exists a need in the tire industry to develop a process for makingtape or strip which can be used as cap plies, breakers and reinforcementin the carcass of tires, which is less capital intensive and less laborintensive than processes of the prior art. Moreover, there needs to be aprocess which produces more uniform tape and which does not producewaste. In addition, it would be desirable to produce a packaged tape orstrip which is ready to apply to a tire as a cap ply or which can beused as breakers and reinforcement in the carcass of tires.

BRIEF SUMMARY OF THE INVENTION

Applicants have recognized that cement flows much better than rubber,and that the use of cement for encapsulating single end cords issuperior to the rubber used in the STEELASTIC® Cap Strip System. Inaddition, applicants have recognized that cement can be applied atambient temperature and ambient pressure, as opposed to rubber in theSTEELASTIC® Cap Strip System, which must be applied in a heatedextruder. Thus, the present invention overcomes the problems associatedwith the prior art by providing a process which does not require the useof extruder dies as in the STEELASTIC® Cap Strip System.

In addition, the process of the present invention is not as laborintensive as the slit rubberized fabric process of the prior art, as itdoes not involve slitting of fabric. In addition, it is not as capitalintensive as the slit rubberized fabric process, as it does not requirea calendar roll. Moreover, the process of the present invention avoidsthe potential for error in that it does not have a slitting step, andhence the possibility of non-uniformity due to the possible varyingnumber of single end cords in each strip is virtually eliminated. Also,since there is no slitting step in the process of the present invention,no edge fray is created and there are no cut cords on the edges of thetape. Thus, the process of the present invention produces less scrapthan the slit rubberized fabric process. Finally, the overall weight ofthe tire could be reduced, since there is no need to add rubber toensure good adhesion of the fabric to the tire rubber.

Therefore, in accordance with the present invention, there is provided aprocess for making a tape from a fabric. The process comprises dipping afabric comprising a plurality of single end cords in a solvent-basedcement that includes an elastomeric composition dissolved in a solvent,and drying the cement so that the majority of the solvent evaporates,thereby forming a tape comprising the fabric encapsulated in theelastomeric composition. The resulting ready-to-apply tape can beproduced to the dimensions of the application, such as a cap ply of tenends.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a portion of the Steelastic® process ofthe prior art for making a tire reinforcing tape from single end cord.

FIG. 2 is a partial elevational view of a portion of the process of thepresent invention for making a tire reinforcing tape from single endcord.

FIG. 3 is a perspective view of the press roll of the present invention.

FIG. 4 is a cut-away, perspective view of a guide roll for guiding thetape in the apparatus of the present invention.

FIG. 5 is a perspective view of the final drive unit of the apparatus ofFIG. 2.

FIG. 6 is a perspective view of a comb for guiding the tape of thepresent invention to a winder.

FIG. 7 is an elevational view of the winder of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

In accordance with the present invention, there is provided an apparatusand a process for making strip, or tape which can be used as cap plies,breakers and reinforcement in the carcass of tires. The process of thepresent invention will be described in the context of the operation ofthe apparatus of the present invention with respect to FIGS. 2-7. Thetape is made from a greige “belt-cord fabric” (as opposed to “tire-cordfabric”), or mini-fabric, which comprises a plurality of single endscords. This belt-cord fabric can be made on a fabric loom, such as afabric loom which is commercially available from Jakob Muller, AG, ofFrick, Switzerland. This machine can be set to make fabric which has awidth smaller than traditional tire-cord fabric used in the slitrubberizerd-fabric process. The width of the greige fabric is the widthof the desired cap ply, typically about ¼″-⅜″. This fabric can be madeby running a plurality of single end cords in the warp direction. Thenumber of single end cords per inch for cap plys or carcass applicationsvaries depending on the cord construction, and for a particularconstruction, depending on the tire type and the tire manufacturer. Aweft yarn is run in the cross-machine direction. The weft yarn is anelastic yarn which is covered with cotton. The purpose of the weft yarnis to keep the single end cords in continuous, pre-determined proximityof one another.

Typical synthetic yarns useful for the cords of the present inventionare made from polyamides, such as 6,6 nylon, 6 nylon, or any copolymersthereof. Alternatively, the yarns may comprise polyesters, aramidfibers, rayon, glass or carbon, etc. A particularly suitable yarn foruse with the present invention is T-728, which is a heat stabilized 66nylon, commercially available from DUSA International of Wilmington,Del. To meet the strength and durability requirements for tireapplications, the yarns are normally prepared from high viscositypolymers containing stabilizers and are drawn at high draw ratios toyield high tenacity yarns, as disclosed in U.S. Pat. No. 3,311,691.

The greige fabric, shown generally at 10 in FIG. 2, enters the apparatusof the present invention. The apparatus of the present inventionincludes a frame having a plurality of vertical beams 12, a pair ofhorizontal beams 14, and a set of braces 16. The greige fabric istypically treated with an activator for bonding rubber to the cords.Typically, a resourcinol-formaldehyde latex (rfl) is used as theactivator dip. This process is not shown as it is a standard industrypractice. The treated fabric is sent to a guide roll 18, which may beoptional, depending on the distance the fabric must travel. The treatedfabric is then sent to a dip station, shown generally at 20 in FIG. 2.Dip station 20 includes a take-out 22, a cement dip pan 24 and amechanism 26 for lifting and lowering the dip pan.

The fabric is dipped in the cement dip pan by the mechanism set forthbelow. As can be seen from FIG. 2 in particular, dip pan 22 includes aplurality of receiving rolls 32. The rolls keep the fabric advancingthrough the dip pan and ensure that the fabric is submerged in the dippan. Rolls 32 include a plurality of crests 32 a as shown in FIG. 4 anda plurality of grooves, or valleys 32 b as shown in FIGS. 3 and 4. Thefabric rests in the grooves 32 b of the receiving roll. A press roll 34is disposed above the middle dip pan roll 32. Press roll 34 includes aplurality of crests 34 a and valleys 34 b. As can be seen from FIG. 4,crests 34 a mesh with the valleys 34 b of receiving roll 32. It shouldbe noted that several strips of fabric may be dipped at one time. Thestrips of fabric stay on the crests of the press roll and in the valleysof the dip pan roll to press the cement into the spaces between thestrips of fabric as they travel through the dip pan. A solvated, or wettape, is shown coming out of the grooves of the dip pan roll at 33 inFIG. 4. If several strips of fabric are dipped, guide rolls may be usedat this point forward in the process to keep the strips of fabricseparate.

Again, variations of the specific equipment used may be made withoutdeparting from the scope of the present invention. For instance, ifthere is enough tension in the fabric as it travels through the dip pan,the use of the press roll may not be necessary. In this case, there justmust be enough tension in the fabric to keep it in the valleys of thereceiving roll of the dip pan. In this case, an appropriate support,such as a guide roll or a glass bar, can be used for the fabric.

The dip that is used in the dip pan is a solvent-based cement. Thissolvent-based cement includes an elastomeric composition, which isdissolved in a solvent, such as toluene. This elastomeric compositionmay comprise, for example, but is not limited to, a natural rubber, or anatural rubber with styrene butadiene or styrene butadiene withpolybutadiene. These constituent materials in the elastomericcomposition may be mixed with reinforcing agents, activators and/orplasticizers, depending on the needs of the end user. The percentage ofsolvents in the cement depends on the speed at which the cords are runthrough the apparatus. This percentage is typically in the range of10-30%.

The solvated, or wet tape is then sent to a guide roll 36 and to anotherguide roll 38 as shown in FIG. 2, and more particularly in FIG. 5. FIG.5 is a cut-away view showing a portion of an exemplary guide roll of thepresent invention. As can be seen from FIG. 5, grooves 40 are formed inthe guide roll for accommodating the solvated tape. It should be notedthat rather than using guide rolls for guiding the tape after it leavesthe dip pan, sleeves may be used around the guide rolls after the dippan. The purpose of either the guide rolls or the sleeves is to keep thetape aligned and to prevent it from rolling as it passes out of theapparatus as shown in FIG. 2.

The solvated tape is then sent to an oven 42, where it goes through onepass, to another guide roll 44, and then another pass through the oven.In the oven, the fabric must be fixed in a single plane. This is done bymaintaining the tension in the fabric, and is necessary to maintain theintegrity of the tape. The cement, including the solvent and theelastomeric composition, are dried in the oven. This drying typicallyoccurs at about 110° C. for some period of time, which is dependent onthe speed at which the greige fabric is being driven through theapparatus. The drying drives off, or evaporates, the majority of thesolvent. What remains is the ready to apply fabric, encapsulated in theelastomeric composition, thereby forming the tape. This tape is shown at46 in FIG. 6. In the final product, some small residual amount ofsolvent remains as a component of the tape. The solvent may comprise0.0009-5% of the weight of the tape.

From the oven, the tape is sent back through guide roll 38, to a seriesof guide rolls, 46, 48 and 50, and to a drive unit, shown generally at52 in FIGS. 2 and 5. Another drive unit 54, including shaft 54 a androlls 54 b and 54 c, is optional, and is used only when drive unit 52 isnot operational. As can be seen from FIG. 2, drive unit 52 includes ashaft 52 a and geared rolls 52 b and 52 c, for driving the tape throughthe apparatus. As shown in FIG. 5, the drive unit is supported in aframe 56, which includes a support bar 58 for presenting the tape as itmoves through the apparatus. The support roll is held between a pair ofsupports 60.

The tape, which is shown at 62 in FIG. 6, is then sent to a pair oftype-two guide rolls, 62 and 64 and to a mechanism 66 for presenting thetape to an optional comb 68 as shown in FIG. 6. Mechanism 66 includesvertical supports 66 a, a horizontal bar 66 b as well as a roller 66 c.The bar and the roller are held together by an end cap 66 d. The taperolls over roller 66 c and is advanced to comb 68. The comb of FIG. 6 issimilar to a comb used in a known single end cord process to keep thecords separated, except that in the comb of FIG. 6 has less teeth, andthe teeth are more widely spaced, than a comb used in a known single endcord process, in order to accommodate the tape. The tape is then sent toa winder 70, which is supported by a framework 72 as shown in FIG. 7.After the winder, the tape is sent to a bobbin 74, where it is wound andstored. A pair of bobbins is shown in FIG. 7.

After the comb, the tape is sent to a guide wheel 76 as shown in FIG. 7.The guide wheel is held onto the framework 72 of the winder by afastener 78. From guide wheel 76 the tape is sent to another guide wheel80. Similar guide wheels can be found in a known apparatus for makingsingle end cord; however, such guide wheels have crests and valleys foraccommodating the single end cords. In contrast, in the apparatus of thepresent invention, the surfaces of both guide wheels 76 and 80 do nothave crests and valleys, but rather are smoothed out to accommodate thetape. The use of such a guide wheel is optional in the presentinvention, and is used to ensure that the tape stays in place. As thetape moves from guide wheel 76 to guide wheel 80 and to the finalpackage (i.e., the winder 70 with tape wound on it), the tension in thetape is maintained by a dancer arm 82. The end of the dancer arm pivotsabout an upper pivot point 84, and about a lower pivot point 86. Themovement of the dancer arm is limited by a lower limit device 88, whichkeeps the dancer arm from hitting against the bobbin. Upper pivot point84 and lower limit device 88 are held against the framework by a plate90, which fastens to the framework of the winder. A guide roll 92 guidesthe tape to a guide 94, through which the tape travels to be presentedto the final package.

With the present invention, because the individual cords are dipped in acement, the cords have better access to the cement than to rubber in theprior art, because rubber does not flow as well as cement. Thus morecomplete coverage of the fabric, and the cords in the fabric can beachieved as compared to processes of the prior art. Consequently, withthe present invention it is possible to produce a superior tape ascompared to the slit fabric or STEELASTIC® Cap Strip System. While itmight be possible to achieve the desired encapsulation characteristicsfor elastomeric compositions such as rubber at high heat and highpressures, the present invention is able to achieve these desiredencapsulation characteristics at ambient temperature and ambientpressure while the cement is being applied.

The tape of the present invention is ready to use as a cap ply for atire. When used in this application, the tape is wound directly onto thetire. The single end cord in the tape then adheres to the rubber in thetire curing process. Alternatively, as noted above, the tape may be usedas a breaker and reinforcement in the carcass of tires. The tape of thepresent invention is generally about ¼″ to ⅜″ wide.

The invention will be described in greater detail with reference to thefollowing example which is intended to illustrate the invention withoutrestricting the scope thereof.

Example

A tape was made using the apparatus of FIG. 2 as described above. Agreige, single weft tire cord fabric made from nylon 6,6 was sentthrough the apparatus to a pre-dip pan where rfl dip was applied. Thedip in the pre-dip pan was made by adding water, sodium hydroxide(NaOH), or caustic pellets, resourcinol flake and formaldehyde to atank. This solution had a solids content of about 6%. The solution wasmixed for approximately 30 minutes. This solution was then aged for aminimum of about 3 hours (minimum of 2 hours, maximum of 4 hours). Inanother tank, a latex was added. Then water was mixed with ammoniumhydroxide, NH₄OH and added to the latex slowly. Then an anti-foamingagent was added and this was mixed slowly. This solution had a solidscontent of about 35%. This solution was then combined with the solutionfrom the first tank. The combined solutions were mixed together forabout 30 minutes prior to use. The fabric was dipped in this combinedsolution for about 3 seconds. The dip was cured at a temperature ofabout 226° C., for a dwell time in the range of 100 and 200 seconds. Thefabric was then sent to another oven, where the dip was cured at atemperature of 165° C. The fabric was then dipped in a mixture oftoluene (85 kg) and a rubber-based elastomeric composition (15 kg). Thetoluene and the elastomeric composition were dried in an oven at atemperature of 110° C., so that the majority of the toluene was drivenoff. A tape which was ½ inch wide was formed.

1. A process for producing a tire cap ply tape wherein the tire cap plytape comprises a width of about ¼ inch to about ⅜ inch, the methodcomprising: a) running a plurality of single end cords in a warpdirection; b) weaving a weft yarn through the plurality of single endcords in a cross-machine direction to form a greige fabric, wherein thewidth of the greige fabric is about ¼ inch to about ⅜ inch; c) treatingthe greige fabric with an activator; d) directing the greige fabric intoa cement dip pan comprising a plurality of receiving rolls and a pressroll wherein the receiving rolls and press roll each comprise crests andgrooves adapted to accept the greige fabric, and wherein the dip pancontains a solvent-based cement comprising a solvent and an elastomericcomposition; e) advancing the greige fabric through solvent-based cementby running said fabric through the rolls of the dip pan whereby thefabric rides through the grooves of the receiving rolls and on thecrests of the press roll to form a solvated tape; f) guiding the tapefrom the dip pan to an oven using at least one guide roll wherein theguide roll comprises grooves for accommodating the solvated tape; g)drying the solvated tape in the oven whereby the majority of the solventevaporates, and the elastomeric composition remains, encapsulating thegreige fabric to form the tire cap ply tape; and h) winding the tire capply tape on a bobbin using a winder wherein the tire cape ply tape isstored on the bobbin.
 2. The process of claim 1 wherein the activatorcomprises resourcinol-formaldehyde latex.
 3. The process of claim 1wherein steps a)-e) are performed at ambient temperature and pressure.4. The process of claim 1 wherein the solvent is toluene.
 5. The processof claim 1 wherein the elastomeric composition is selected from thegroup consisting of natural rubber, a natural rubber with styrenebutadiene or styrene butadiene with polybutadiene.
 6. The process ofclaim 1 wherein the weft yarn is an elastic yarn.
 7. The process ofclaim 1 wherein the weft yarn is covered with cotton.